DE4023660C2 - Flow control valve for a vehicle brake system - Google Patents

Description

The invention relates to a flow control valve for a vehicle Brake system according to the preamble of claim 1.

Anti-lock vehicle braking systems (ABS) according to the status of technology have to control the brake pressure in the brakes of the vehicle mainly two solenoid valves. A currentless Open valve is in the line from the master cylinder to Brake arranged and allows unimpeded pressure over wear during "normal braking", d. H. without the intervention of Anti-lock device. Furthermore, a currentless is closed senes valve provided that when the anti-lock rain drainage of brake fluid from the brake into one Storage space (so-called expander) enables.

Will be with such an anti-lock vehicle brake If braking was carried out without the risk of locking, none is carried out of the two solenoid valves supplied with current. He follows on the other hand, an ABS control, both valves are actuated, on the one hand the hydraulic connection between the main brake cylinder linder (the pressure source) and the brake to interrupt and around on the other hand, this reduces the brake pressure in the brake to allow hydraulic fluid from the brake cylinder can escape. As soon as the braked, initially blocking tendency pointing wheel again comes into a slip area, the one allows stronger braking, the function of the valves in changed in a known manner.

It is known in the prior art to use the valves and especially the one that controls the pressure increase in the brake To operate the valve clocked, d. H. the valve gets high Frequency opened and closed to adjust for optimal ABS control to the given braking conditions set the desired pressure increase gradient in the brake  can. The increase in pressure is determined by the ratio of Valve on and off times controlled.

Such a clocked valve control is not only in terms of problematic of the tax accuracy (the correlation of the mechanical behavior of the valve to the time sequence of the electri signals depends on the state of the valve), but also causes annoying side effects for the driver of the Vehicle that can lead to irritation. So can a pulsed operation of ABS valves a pulsation of the Brake pedals result, as well as a hydraulic feedback on all components, even those with a nuisance can go hand in hand.

The clocked operation of ABS valves has both techni cal disadvantages regarding the accuracy of the pressure control as well as disadvantages regarding the comfort of the brake.

It is also known in the prior art, a so-called Flow control valve instead of the above, de-energized open valve. Such a flow regulator valve regulates an orifice differential pressure a spring force in relation to a surface. This state of the However, technology has the disadvantage that it is not possible a so-called without expensive additional facilities To set the "pressure maintenance phase", that is a time span in which the pressure of the hydraulic fluid in the brake is not is increased and is not noticeably lowered.

Furthermore, such known flow control valves have the Disadvantage that they only have a pressure increase in the brake allow a predefined rise gradient.

EP 0 344 544 A1 describes an anti-lock vehicle known brake system in which two valves functionally in Series are connected, namely a purely mechanical actuated valve between the master brake cylinder (as Pressure source) and the brake and on the other an electromagnetic  cal valve between the brake and a hydraulic fluid receiving space (i.e. for draining brake fluid the brake if there is a risk of locking). The electromagnetically operated The valve therefore does not control the pressure increase in the brake and also does not allow adjustment of the pressure increase level served.

The invention is based on the task of a flow control valve to be provided for an anti-lock vehicle brake system len, in a simple manner and without irritating the driver an adjustment of the pressure rise gradient enables. The Flow control valve should be simple.

This task is based on a flow control valve type mentioned solved in that an electromagnetic cal device one of the spring force loading of the valve member opposing force controlled on the valve member brings.

According to the invention is therefore a known "Flow regulator valve" further developed in that the Ven The spring force acting a controlled electromagnetic generated force is superimposed with the balance of forces on the valve member and thus the flow through the valve can be influenced, and this valve is called a flow control valve used for a vehicle brake system.

In this way, the valve regulates the one per unit of time The amount of liquid flowing through automatically depending on of a reference surface, an aperture and a spring force and on the other hand by means of an additional, external control a current, which the spring force on an anchor of the Valve counteracts through the electromagnetic device the rate of pressure increase (pressure gradient) on the brake optionally adjustable without increasing the pressure of one Control cycle the valve must be operated clocked.  

According to a preferred embodiment of the invention is provided see that the electromagnetic device actuates an anchor in which a passage is formed, the position of which in with respect to one in a stationary component of the valve shaped passage determines the flow cross-section mentioned.

In order without additional complex valves or others Control devices as many functions as possible for the control of being able to combine the brake pressure in a single valve, is according to a further embodiment of the inventive concept provided that more in the anchor and the fixed component Passages are formed through which when the valve is at Tendency to block the connecting line between the pressure source and the brake closes, an open hydraulic connector line from the brake to a hydraulic fluid takes up space.  

According to the invention, the valve can be designed in such a way that the armature moves in one direction with increasing current flowing through the electromagnetic device and successively reaches at least the following positions:

• - A first position in which the flow cross section in the hydraulic line between the pressure source and the brake is maximum and the hydraulic line between the brake and the hydraulic fluid receiving space is blocked,
• - A second position in which the flow cross section in the hydraulic line between the pressure source and the brake is smaller than the specified maximum value and the hydraulic one Line between the brake and the hydraulic fluid taking space is locked,
• - A third position in which the hydraulic line between the pressure source and the brake as well as the hydraulic line between the brake and the hydraulic fluid receiving Space are locked, and
• - A fourth position in which the hydraulic line between the pressure source and the brake is locked while the hydrau cable between the brake and the hydraulic fluid receiving room is open.

Exemplary embodiments of the invention are described below with reference to Drawing described in more detail. It shows:

Fig. 1 shows schematically a section through a first example of a Ausfüh approximately a valve for a blockierge protected vehicle brake system;

FIG. 2 through 4, a further embodiment of the valve according to Fig. 1 in different operating states ver.

The valve shown for an anti-lock vehicle brake system has a valve body 10 . An inlet 12 leads into the valve body 10 and is connected to a master brake cylinder (not shown) of the brake. A pressure in the hydraulic fluid is generated in the master brake cylinder by pedal actuation and propagates in the direction of arrow P ₁ via the inlet 12 into the valve body 10 .

Furthermore, the valve body 10 has an outlet 14 which leads to a brake (not shown) in order to transmit pressure in the direction of the arrow P ₂ to the brake.

An electromagnetic device for controlling the valve has a coil 16 which is supplied with currents of different currents. The coil 16 moves an armature 18 in the valve body 10.

In Fig. 1, the armature 18 is pressed to the left by a coil spring 20 . When current flows, the coil 16 exerts a force on the armature 18 which is directed to the right in FIG. 1, that is to say counteracts the spring 20 .

If no current flows through the coil 16 , the spring 20 pushes the armature 18 in FIG. 1 to the left as far as possible (further to the left than is shown in FIG. 1) and an axially aligned channel 22 through the valve body 10 projects beyond a radial one From section 22 'in conductive connection with an annular space 26 which rotates in a central bore of the armature 18 . Furthermore, the outlet 14 of the valve leading to the brake is also in conductive connection with the annular space 26 via an axial channel 24 and a radial section 24 ′ of the channel, so that hydraulic fluid flowing into the inlet 12 with a maximum flow cross section, ie completely unimpeded, from the inlet 12 in the direction of arrow P ₁ to exit 14 in the direction of arrow P ₂ . This is the case with a so-called "normal braking", that is, when it is established in a known manner that there is no tendency for the wheel to lock and therefore no ABS control is required.

The valve shown in Fig. 1 enables different operating conditions with current flow through the coil 16 depending on the strength of the current. Fig. 1 shows a state of the valve in which a relatively small current flows through the coil 16 , which shifts the armature 18 to the right against the force of the spring 20 so that the annular space 26 in the armature 18 the radial portion 22 'of the channel 22 overlaps only very slightly, that is, there is a narrow restriction in the flow path from channel 22 to channel 28 . In this position, the above-mentioned throttle point defines the flow cross section from the inlet 12 to the outlet 14 , since the radial section 24 ′ of the channel 24 is no longer connected to the annular space 26 , as is shown in FIG. 1.

In the state of the valve shown in Fig. 1 hydraulic fluid flows from the radial section 22 'of the channel 22 past a so-called control edge 40 into the annular space 26. The flow takes place in the direction of the arrows shown and the flow rate per unit of time is determined by the relative position between the control edge 40 and the channel section 22 'be true, which adjusts itself depending on the pressure prevailing at the inlet 12 . Hydraulic fluid flows in the direction of the arrows through the channel 28 into a gap 32 between the armature 18 and the valve body 10. The gap 32 does not restrict the flow. The hydraulic fluid flows further in the direction of the arrows in an end space 34 in the valve body 10 and from there in the direction of the arrow in a throttle 36 and from there into an interior 38 in the armature 18. From the interior 38 , the channel 24 leads to the outlet 14 of the Valve.

The throttle 36 causes a difference in the pressure in the hydraulic fluid in the end chamber 34 on the one hand and in the nenkammer 38 on the other. In the space 30 of the spring 20, the same pressure is given, as in the end region 34. Thus, the Durchströmmenge said generated of the hydraulic fluid back pressure across the restrictor 36, which multiplied by the area of the end space 34, a force on the armature 18 results in that in Figure acts. 1 from left to right, as against the force of the spring 20 acts. The system is self-regulating: flows too much Hydrau likflüssigkeit via the control edge 40, the channel 28 and the gap 32 in the front chamber 34, so builds up between the front space 34 and the interior 38 due to the throttling 36, a relatively large pressure differential and dependent of the diameter D _{i of} the interior 38 , this pressure difference generates a force on the armature 18 which is directed to the right in FIG. 1 and thus also shifts the annular space 26 with the control edge 40 to the right and thereby reduces the flow cross section, so that the pressure difference between Front space 34 and interior 38 becomes smaller and the valve thus automatically regulates the flow rate of the hydraulic fluid. In addition to the geometrical dimensions of the effective area for the hydraulic forces, in particular the inner diameter D _{i of} the interior 38 , the force of the spring 20 and the strength of the flowing through the coil 16 are decisive for the amount of hydraulic fluid flowing over the control edge 40 per unit time electrical current, which counteracts the spring force. The stronger the current, which can be varied between about 0 and 2 A, the weaker the resulting force which pushes the armature to the left, so that smaller pressure differences resulting from smaller flow rates, the armature in the area of the control edge 40th move. The internal control loop thus independently regulates a quantity that generates a dynamic pressure at the throttle 36 , which multiplied by the area of the end space 34 results in a force that corresponds to the spring force minus the magnetic force on the armature. Thus, with increasing electrical current through the coil 16, the pressure rise gradient for a pressure transmission from the input 12 to the output 14 can be reduced. If the electrical current through the coil 16 is further increased, the armature 18 in FIG. 1 is finally pushed to the right against the force of the spring 20 to such an extent that it abuts a stop and at the same time all connections between the input 12 and the output 14 interrupts so that there is no more pressure transmission from the master cylinder to the brake.

The valve according to the invention thus has two throttling points lying in series in the flow path of the hydraulic fluid from the pressure source to the brake, one throttling point being freely adjustable with regard to its flow cross section. Thus, depending on the strength of the current flowing through the coil 16 , the valve enables three functions: 1. a free passage for the hydraulic fluid, 2. a blockage of the passage from the master brake cylinder to the brake, and 3. the adjustment of a regulation of the flowing amount of hydraulic fluid, where at the flow rate per unit of time is independent of the pressure difference between the input 12 and output 14 of the Ven valve and is only dependent on the current flowing through the coil 16 , the force of the spring 20 , the size of the throttle 36 and the size of the area Forehead 34.

Figs. 2 to 4 show a further development of the presented in FIG. 1 Darge valve, wherein corresponding components are designated by like reference numerals. The valve according to FIGS. 2 to 4 also allows hydraulic fluid to be drained from the brake into a container holding hydraulic fluid (so-called expander) in addition to the above three functions. The valve shown in FIGS . 2 to 4 has a stationary component 44 inserted into the valve body 10 , in which a large number of channels and passages are formed in order to enable the various functions of the valve.

In addition to the channels 22 and 24 already described including their function, an annular channel 46 is provided which connects the interior 38 with the gap 32 . A radially extending channel 48 passes through the stationary component 44 and is connected to the axial channel 24 .

In addition to the input 12 already described (connection to the master brake cylinder) and to the output 14 (connection to the brake), a further output 50 is provided in the valve body 10 , which leads to a space that holds hydraulic fluid (“expander”; not shown). Such spaces are known as such in the prior art. Is the armature 18 in a corre sponding position ( Fig. 4), then leads an open hydraulic line cal brake from the brake via the connection 14 (which now serves as an input) via the channel 24 , the end space 34 , the annular gap 32nd , the ring channel 46 and the channel 52 to the outlet 50 , so that hydraulic fluid can be transferred from the brake (not shown) to the hydraulic fluid receiving space (expander).

In Figs. 2 to 4, a movement of the armature 18 is shown from left to right, in each case an increasing current flows through the coil 16 and the armature from the valve different functions are executed in each of the positions shown.

In the position shown in Fig. 2, the armature 18 is furthest to the left. No current flows through the coil 16. It is understood that the armature 18 is prevented by a stop (not shown ge) from being pressed completely against the left end wall 54 of the housing by the spring 20 . An end space 34 between armature 18 and end wall 54 is thus left free for receiving hydraulic fluid. Hydraulic fluid under pressure flows unthrottled from the master brake cylinder (not shown) via the inlet 12 into the channel 22 and from there via the section 22 ′ (without throttling) into the space 30 in which the spring 20 is arranged. Via the space 30 , the hydraulic fluid enters the gap 32 and from there via the ring channel 46 into the interior 38. From there, the hydraulic fluid passes freely through the channel 24 and the outlet 14 to the brake (not shown). The state of the valve according to FIG. 2 thus corresponds to "normal" braking, that is to say without anti-lock control.

Fig. 3 shows a state of the valve in which an electric current flows through the coil 16 and the armature 18 is shifted to the right against the force of the spring 20 . The function of the valve according to FIG. 3 corresponds to the function of the state shown in FIG. 1, ie the control edge 40 overlaps the opening of the section 22 'of the channel 22 up to a narrow throttle gap, so that the self-regulation described above is per time Unit let-through amount of liquid depending on the only variable, the current flowing through the coil 16 , it follows. The flow path of the hydraulic fluid thus leads from the inlet 12 via the channel 22 , the channel section 22 ', the control edge 40 , the spring chamber 30 , the annular gap 32 , the end chamber 34 , the throttle 36 to the interior 38 , the pressure difference due to the throttle 36 from the front space 34 to the interior 38 , which presses the armature 18 to the right against the resulting force (spring 20 minus magnetic force) in FIG. 3, as described above with reference to FIG. 1. In this state, the outlet 50 is completely separated from the other channels and passages.

If the strength of the current flowing through the coil 16 is varied, the resulting force on the armature 18 is correspondingly weakened to a greater or lesser extent, so that the armature reaches the control edge at a smaller pressure difference, which in turn occurs with a smaller flow rate through the throttle 36 , and that internal control loop closes, so that the amount of liquid left per unit time is a function of the current of the coil 16 . The pressure increase gradient when a brake pressure is built up in the brake can thus be set as a function of the coil current.

If the electrical current through the coil 16 is increased so far that the spring force is exceeded by the magnetic force, the control edge 40 moves beyond the channel section 22 'and it reaches the state shown in FIG. 4, in which the hydraulic fluid from the input 12 only reaches the end of the channel section 22 'and is blocked off there. Instead, brake pressure from port 14 in the direction of arrow P ₄ to output 50 can be built. For this purpose, hydraulic fluid passes from the connection 14 via the channel 24 into a radially extending channel 48 and from there via a further channel 46 in the armature 18 and the gap 32 aligned with the channel 48 and the gap 32 into the end space 34 and from there again via the annular channel 46 into one Section 52 'of a further channel 52 , which extends axially through the stationary component 44 . From there, the hydraulic fluid passes via a further radial section 52 ″ of the channel 52 to the outlet 50 , which leads to a space receiving hydraulic fluid. Parallel to the flow path described above via the channels 46 and 48 , a flow also takes place directly from the channel 48 , as shown in FIG via the interior 38 to the channel 52.

Claims (5)

1.Current control valve for a vehicle brake system, the flow cross-section of which is continuously adjustable between a closed position and a position of maximum hydraulic cross-section, with a spring-loaded valve member and with a throttle, which generates a differential pressure acting on a reference surface of the valve member, from which one of the spring force loads Valve member opposing force results in such a way that the amount of fluid flowing through the flow control valve per Zeitein unit is automatically regulated as a function of the spring force load, the reference surface and the throttle, characterized in that an electromagnetic device ( 16 ) controls a force directed in opposition to the spring force load of the valve member onto the valve member. 2. Flow control valve according to claim 1, characterized in that the valve member is an electromagnetic device ( 16 ) associated armature ( 18 ) with a passage formed therein ( 28 ), the position of which in relation to a in a stationary component ( 10 , 44 ) the flow control valve existing passage ( 22 ') sets the flow cross section through a closed control loop. 3. Flow control valve according to claim 2, characterized in that the throttle ( 36 ) is formed in the armature ( 18 ). 4. Flow control valve according to claim 2 or 3, characterized in that in the armature ( 18 ) and the ortsfe most component ( 10 ; 44 ) further passages ( 46 ; 48 ; 52 ; 52 ') are formed, through which when that Flow control valve blocks the connection between the pressure source and the brake, a fluid connection ( 14 , 24 , 48 , 46 , 43 , 52 ', 44 , 52 ", 50 ) leads from the brake to a hydraulic fluid receiving space. 5. Flow control valve according to claim 2 or 3, characterized in that the armature ( 18 ) with increasing current flowing through the electromagnetic device ( 16 ) moves in one direction and thereby successively reaches at least the following positions:

• 1. a first position in which the flow cross-section ( 24 ', 26 ; etc.) in the hydraulic line between the pressure source and the brake is maximum and the hydraulic line between the brake and the hydraulic fluid-receiving space is blocked,
• 2. a second position in which the flow cross-section in the hydraulic line between the pressure source and the brake is smaller than the said maximum value and the hydraulic line between the brake and the hydraulic fluid-receiving space is blocked,
• 3. a third position in which the hydraulic line between the pressure source and the brake and the hydraulic line between the brake and the hydraulic fluid receiving space are blocked, and
• 4. a fourth position in which the hydraulic line between the pressure source and the brake is blocked, while the hydraulic line between the brake and the hydraulic fluid receiving space is open.